Error after update Emotion to version 11

[mheob]

Emotion has breaking changes in version 11, so the @emotion/core package is no longer available.

After updating my project I get this error:

../../node_modules/react-portal-overlay/index.es.js:1:0
Module not found: Can't resolve '@emotion/core'
null

I would be happy if this nice plugin would also get the support for Emotion 11.

[rbhlrn]

please fix